Please help, I do not understand what the problem is. Why do we "have" to use a void method when a static method could be used as well? It returns the same thing

Question about the task

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package en.codegym.task.pro.task10.task1005; /* Serial entrepreneur */ public class Building { private String type; public static String initialize(String type){ return type; } public static void main(String[] args) { Building building = new Building(); building.initialize("Barbershop"); } }

A building was constructed with the expectation that it would be used as a restaurant, but the owners later decided to remodel the space for use as a barbershop. We need to ensure that the building is a versatile space whose purpose can be changed without constructing a new building.
To do this, create an initialize method that assigns a value to the type field (which determines the type of building), and remove the constructor.

Requirements:

The Building class must have a private String field called type.
There should be no constructors declared in the Building class.
The Building class must have a public non-static void initialize method with a String parameter.
The type field must be initialized in the initialize(String) method.

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Thomas

Level 41 , Bayreuth, Germany

17 July, 08:56

You're mixing up different things. If you add the static modifier to a method definition, then this means, you can call this method from every context. From a static method or from within an instance method. A non static method can just be called from an existing object. On the other hand there are modifiers that define the return value, that modifier you have to set, like int, double, Object, String or, if no value should be returned, void. So void means, you do not return a value, all is done within that method. static means, you can invoke the method without needing to create an object of the class that the method contains first. Here you're supposed to call a method to create an object. Means the object does not yet exist. And that means you have to invoke a static method (a method that you can call without the need to create an object first). Within that method you create a Building object and set it's (instance) variable type. Because you set the type using the instance variable the task writers decided the initialize method does not need a return value. In the end the behaviour of a constructor is imitated. A constructor is implicit static void, too. I don't know if you already know about constructors but I add a little code example using one to show the difference between static and non static methods/ variables.

Thomas

Level 41 , Bayreuth, Germany

17 July, 08:56

public class SID { // StaticInstanceDifference
    // instance variable
    public String iv;

    // static (class) variable
    public static String cv;


    // constructor, setting the instance variable with some value
    public SID(String iv) {
        this.iv = iv;
    }

    // instance methods printing instance and class variables
    public void printIv() {
        System.out.println(iv);
    }

    public void printCv() {
        System.out.println(cv);
    }

    // static method, just has access to static (class) variable
    public static void staticPrintCv() {
        System.out.println(cv);
    }

    // testing...
    public static void main(String[] args) {
        // creating objects, each has its own set of instance variables.
        SID o1 = new SID("first object's variable");
        SID o2 = new SID("first object's variable");
        // each object has a different value for iv
        o1.printIv();
        o2.printIv();

        // does not work, without an object an instance method or variable can not be accessed
        // printIV();
        // SID.printIV();

        // now setting a class variable
        cv = "class variable";
        // it does not matter from what context to access it (class or object, instance or static), it always has the
        // same value

        staticPrintCv();
        o1.printCv();
        o2.printCv();
        System.out.println(SID.cv);
        System.out.println(cv);

        // if we change the class variable value, it changes of course for all these above ways to access it
        cv = "class var changed";
        staticPrintCv();
        o1.printCv();
        o2.printCv();

        // changing an instance var, it changes just for that object and not for all
        o1.iv = "first object's variable cahnged";
        o1.printIv();
        o2.printIv();
    }
}

Guadalupe Gagnon

Level 37 , Tampa, United States

17 July, 15:04

Just a little correction. The initialize method is not supposed to create a new object, it is supposed to take an already created object and set it to a valid state. This is why the method can not be static (it needs an object instance) and, because it is setting the state and not returning anything, it should be void.

Gummy C

Level 11 , United States of America, United States

19 July, 14:47

Thank you for the explanation, it took me a long time. But, I finally understand what you are saying about creating an object within the main method rather than creating the object prior. Thanks again

Gummy C

Level 11 , United States of America, United States

19 July, 14:47

Thanks for the response as always. You are always answering my questions. Your input helped a lot in understanding.